Monarch Migration in Oregon: 2026 Timing

The autumn southbound movement through Oregon typically builds from July 12, peaks around August 2, and thins out by November 1. That window is derived from 419 research grade iNaturalist records of adult monarchs in Oregon, divided by all observations in the state in the same week so it measures butterflies rather than how many people were outdoors. Monarch Watch, which models the migration from recovered tagged butterflies, puts the midpoint at latitude 43 at Sep 11. The Monarch Watch latitude table describes the eastern migration, the one that ends in Michoacan. Oregon monarchs belong to the western population and fly to the California coast instead, so their row is shown here for scale and is not a check on this state. There is no equivalent published latitude model for the western migration that we could find.

Adult monarchs are typically being recorded again in Oregon from about May 10, and are established by May 31. Spring is not one arrival the way autumn is one departure. USFWS states that "As temperatures warm at the overwintering sites in the spring, monarchs begin to breed and lay eggs on milkweed throughout their spring journey." so the butterflies that reach Oregon in spring are usually the children or grandchildren of the ones that left it last autumn, not the same individuals.

Not in the legal sense, and this gets stated wrongly almost everywhere. US Fish and Wildlife Service proposed listing the monarch as threatened on December 12, 2024, with a section 4(d) rule and proposed critical habitat. As of Aug 24, 2026, no final rule has been published, so there is no federal listing in Oregon or anywhere else. The monarch is very widely described online as endangered. Under United States law it is not. The International Union for Conservation of Nature, which is a different body with no legal force in the US, assessed the migratory monarch separately, and its assessment has itself been revised. Those two things get merged constantly. This site states the federal position and names it as the federal position.

The milkweeds actually recorded in Oregon most often are showy milkweed (Asclepias speciosa), narrowleaf milkweed (Asclepias fascicularis), heartleaf milkweed (Asclepias cordifolia), humboldt mountains milkweed (Asclepias cryptoceras). Xerces states: "The Xerces Society recommends planting milkweed species that are locally native and for which regionally-sourced seeds and plants are available." That list is what the observation record says grows here, which is a reasonable starting point for what is locally native, and the Xerces Milkweed Seed Finder will tell you who sells seed of it.

From about October 28 onward, which is roughly this state's median first freeze. Xerces states: "In most regions, fall planting is a good approach because the seeds' exposure to cold, moist conditions during winter and spring will help stimulate germination." So the fall sowing date is not a separate fact to look up, it is your frost date. Oregon's median first freeze is October 28 according to NOAA normals for representative stations. Xerces also states: "Following site preparation to remove weeds, seeds can simply be scattered onto the soil surface by hand."

Because a sightings map and a typical window are different objects. Journey North plots what volunteers reported this year, live, which is the right tool for "where is the front today" and which we link to on this page. This page publishes what usually happens in Oregon, from the observation record, so it can answer the question before this year's sightings exist. Two corrections move our dates away from the numbers you would get from a raw record count. Records are restricted to adults, because larvae and eggs peak weeks earlier: the unfiltered Oregon curve peaks in June and the adult curve peaks in June. And counts are divided by all observations in Oregon that week, which removes the effect of how many people were outdoors with a phone.

California. Oregon is west of the Rockies, and USFWS states that "The western population overwinters in hundreds of groves (clusters of trees) along the California coast and into northern Baja California, Mexico." The Xerces Society counts those groves every winter; the most recent counts it published are on our hub page.

No, and the numbers say so consistently. Regular adult monarch records in Oregon run to about November 1, while the state's median first freeze from NOAA normals is October 28, 4 days earlier. That pattern holds in every state on this site, which is why the practical advice is not to cut the garden back at the first frost. A first freeze is a light radiational frost, not the hard freeze that ends a season, and the autumn generation is still moving through on its way to the California coast. Late nectar in Oregon is doing real work well past October 28.

No. That table describes the eastern migration, the one that ends in central Mexico. Oregon monarchs belong to the western population and fly to the California coast instead. The nearest row is shown for scale and marked as not applicable; no equivalent latitude model is published for the western migration.